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Biomedical subjects

T Albrektsson

Publications and source records attributed to T Albrektsson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Histologic evaluation of guided vertical ridge augmentation around implants in humans.

Recent experimental and clinical case reports demonstrated vertical ridge regeneration in atrophic posterior mandibles and maxillae. Although the results from these clinical cases are quite encouraging there is a lack of human histologic data on the newly regenerated tissue around commercially available titanium implants. The aim of the present study was to perform a qualitative and quantitative histologic analysis of the bone response to previously exposed implant threads after treatment with guided bone regeneration in a series of patients. A total of 30 Nobel Biocare implants were consecutively placed in 6 patients with partially edentulous mandibles. Of these implants, 6 were planned for removal after 1 year, whereas the remaining 24 implants were inserted to function as support for a fixed partial denture. The 6 experimental implants were intentionally allowed to protrude occlusally 5 to 7 mm from the bone crest without counter-sinking. The exposed implant threads were completely covered by autogenous bone chips. After a 12-month healing period the 6 experimental implants were removed with trephine burs. Bone-to-metal contact and bone density in the implant threads were measured. Clinically, all implants were stable and there was complete tissue fill of the space underneath the membranes. Histologically, a substantial amount of new bone had formed underneath the membrane in all cases. Histomorphometrically, there was a lower bone-to-metal contact percentage in the exposed compared to the nonexposed region in every case. With respect to bone density, there was a mean of 43.2% in previously exposed regions compared to 60.3% in previously nonexposed regions.

Adult↗
PubMed1998

Application of synchrotron radiation in investigation of metal-ion release from a hip replacement prosthesis.

The aim of the present study was to measure very low concentrations of Al, V, Fe, Cr and other metal elements in a matrix of P, S, Cl, Ca and other constituent elements of the human body. These metal elements were released from a failed total hip replacement prosthesis into the surrounding tissues. The experimental results have been compared with those from proton-induced X-ray emission spectroscopy of the same specimen.

Journal Article↗
PubMed1998

The effect of hyperbaric oxygen treatment on bone tissue reactions to c.p. titanium implants placed in free autogenous bone grafts. A histomorphometric study in the rabbit mandible.

This study aimed to investigate the effect of hyperbaric oxygen (HBO) therapy on the tissue reactions to commercially pure (c.p.) titanium implants placed in free autogenous bone graft by a 1-stage procedure. Eighty c.p. titanium implants were placed in the bone grafted from iliac crest to bilateral mandible of 40 Japanese white rabbits without tapping. Twenty rabbits underwent daily a HBO treatment for 60 min under 2.4 ATA during 20 consecutive days and the other untreated 20 rabbits served as controls. The implants with surrounding bone tissue were retrieved 20, 30, 60, 90 and 120 days after surgery, fixated, dehydrated and embedded in resin. About 20 microns thick ground sections were prepared prior to microscopical observations. The bone area and the bone-to-implant contact inside the threads were calculated separately in the grafted bone and in the host bone for each implant. After 30 and up to 120 days, the HBO treated group showed more bone-to-implant contacts in the grafted bone as compared to the non-HBO treated group. In the host bone there were no differences observed between HBO and non-HBO treated groups. This study indicated that HBO treatment was beneficial for the tissue incorporation of c.p. titanium implants when placed immediately in free autogenous bone grafts.

Animals↗
PubMed1998

Quantitative and qualitative investigations of surface enlarged titanium and titanium alloy implants.

Screw shaped implants of commercially pure (c.p.) titanium and titanium-6aluminum-4vanadium (Ti6A14V) were blasted with particles of TiO2 of mean sizes of 25 microns (Group I) and 75 microns (Group II) and inserted in rabbit bone for 3 months. The surface roughness of the implants was examined and quantified with an optical scanning 3-dimensional instrument (TopScan 3D system), revealing the two alloy surfaces in each group had similar surface roughness. Biomechanical (removal torque) tests showed the c.p. titanium implants to be significantly more stable in the bone bed than those of Ti6A14V. In Group I, the c.p. titanium implants demonstrated a mean removal torque of 38 N cm while the Ti6A14V demonstrated a mean removal torque of 27 N cm (P = 0.004). Group II implants revealed a mean removal torque of 70 N cm for the c.p. ti and 50 N cm for the alloy samples (P = 0.003). The removal torque values were converted to shear forces/strengths by three calculation methods, based on (a) the entire length of the implant surface in the cortical region, (b) the thickness of the cortical bone measured in close vicinity to the thread peaks and (c) the bone-metal contact length measured on the non-unscrewed neighbouring implants. Group I: (a) the c.p. ti implants revealed a mean shear force of 4 vs a mean of 3 N/mm2 for the alloy samples. Shear strengths based on (b); were 8 for c.p. ti vs 6 N/mm2 for the alloy. The mean shear strength/force if calculated according to (c) revealed 23 for c.p. ti vs 18 N/mm2 for the alloy. Corresponding numbers for Group II; (a) c.p. ti 8 compared to 6 N/mm2 for the alloy, (b) c.p. ti demonstrated a mean value of 17 vs 11 N/mm2 for the alloy. According to method (c); c.p. ti had a mean shear strength of 26 vs 22 N/mm2 for the alloy samples. Histomorphometrical comparisons were performed on 10 microns thick undecalcified ground sections in the light microscope. In both Group I and Group II, the calculations of the mean bone-to-metal contact demonstrated more bone in contact to the c.p. titanium implants than to the Ti6A14V ones. Whereas comparisons of the bone volume inside the threads demonstrated slightly higher bone volumes around the alloy samples, no statistically significant difference was obtained between the two materials histomorphometrically.

Alloys↗
PubMed1998

Effect of loading on bone regenerated at implant dehiscence sites in humans.

Few investigations have studied the long-term fate of bone formed following the technique of guided tissue regeneration. The aim of the present study was to evaluate bone fill around implant fixtures with dehiscence defects and to study its response to loading. Ten patients were treated with overdentures supported by 2 fixtures ad modum Brånemark. A third 7 mm x 3.75 mm diameter fixture was placed for the purposes of the study in the most anterior part of the mandible with a dehiscence defect of 4 to 5 mm on the buccal aspect (and 3 to 4 threads exposed) which was covered with a Gore-Tex membrane and buried beneath the mucosa. Fixtures were exposed after 5 months (stage 2), ball abutments connected and loaded through an overdenture for 1 year. Nine fixtures were functioning well after 1 year of loading, 6 of which were retrieved with a trephine for histological examination and compared with 6 unloaded fixtures retrieved in our previously reported study. The bone area filling the thread profiles (BA%) and the bone to metal contact (BMC%) were measured in the 3 most apical and 3 most coronal thread profiles on the buccal and lingual surfaces. Statistically significant higher BMC% (P < 0.01) were observed in loaded fixtures in the apical regions (buccal: loaded 51%, unloaded 25%; lingual: loaded 49%, unloaded 24%). Differences approached significance for the regeneration site (loaded 22%, unloaded 6%) but were no different for the coronal lingual region (loaded 28%, unloaded 20%). There were no differences for BA%. This study confirms that there is an increase in bone to metal contact with time and following fixture loading and that this may also occur with bone regenerated under Gore-Tex membranes.

Adult↗
PubMed1998

A volumetric study of guided bone regeneration around titanium implants in the New Zealand white rabbit.

Previous studies have shown the ability for bone to grow under occlusive membranes. This study was undertaken to determine the time required for bone to form in the space created under the membrane and to determine the amount of bone that may be grown under the membrane. Thirty-two New Zealand white rabbits were divided into three groups. A Brånemark implant, having a diameter of 3.75 mm with a length of 7 mm, was placed in each tibia and Gore-Tex membrane was draped over the implant on the experimental side and tethered to the wound margin. Sixteen rabbits were sacrificed at six weeks, eight at twelve weeks, and eight at eighteen weeks. At six weeks the available space under the membrane was filled to 68 per cent, at twelve weeks it was 45 per cent, and at eighteen weeks 54 per cent. A comparison of bone height measurements on test and control sides showed a significant difference (p = 0.0001) at the three time intervals. A comparison of grown bone volumes (test vs control) was also statistically significant (p = 0.0001). The ability to grow bone under an occlusive membrane was confirmed but the long-term survival rate and ability to support load needs to be investigated.

Analysis of Variance↗
PubMed1998

Surface structure of retrieved ICLH femoral cups.

We characterized the surface structure of 21 retrieved femoral ICLH cups, as an indirect measure of surface damage, with an optical scanner specially developed for surface roughness measurements. 3 unused cups were measured and served as controls. The mean insertion time was 10 (5-15) years. 5 areas on each cup were measured, 1 on the top and 4 at the edge. The mean value of 3 different, commonly used, surface roughness parameters was calculated for the edge measurements. We found no correlation between the surface topography and clinical patient data such as age, body-weight, head-shaft angle, implantation time and wear of the polyethylene socket.

Aged↗
PubMed1998

Removal of titanium implants from the temporal bone: histologic findings.

OBJECTIVE: This study aimed to evaluate the histologic examination of bone tissue surrounding three titanium implants, which were removed since the patients presented with long-standing pain in the implant area. The histologic examination was both qualitatively and quantitatively performed. Furthermore, could an explanation be obtained for the pain in the implant area, which, after removal of the percutaneous implant, disappeared immediately? STUDY DESIGN: Retrospective case review; clinical histomorphometric. SETTING: University Hospital Nijmegen, Göteborg University, Sweden. PATIENTS: Three patients of a consecutive series of 189; 1 man and 2 women who had received a bone-anchored, percutaneous, skin-penetrating, commercially pure titanium implant in the temporal bone, on which a transducer was mounted. The implants were removed because of pain in the implant area from the three patients after 31 months, 18 months, and 8 months, respectively. MAIN OUTCOME MEASURES: The percentage of direct bone-to-metal contact was 81%, 59%, and 42%, respectively. The percentage of bone volume between the threads of the screw was 90, 78, and 75, respectively. RESULTS: The qualitatively histologic findings showed no major differences among the three investigated samples. Quantitatively, the amount of osseointegration depended on the duration of implantation. CONCLUSIONS: Direct bone-to-metal contact and the bone volume between the threads increased as the implantation time increased. No explanation was found for the longstanding pain in the implant area and the relief of pain after removal of the percutaneous implant.

Adult↗
PubMed1998

Gothenburg osseointegrated hip arthroplasty. Experience with a novel type of hip design.

The culmination of more than 10 years of laboratory and clinical research has been the clinical trial of a novel hip arthroplasty for osseointegration. The femoral component of this Gothenburg hip is a neck retaining, threaded fixture with rotational symmetry, produced in commercially pure titanium with a specific surface texture. Proximally, a standard orthopaedic taper trunnion mates with a 28-mm diameter zirconia head that articulates against the acetabular component. The latter is also of textured commercially pure titanium, encapsulating a thick ultra high molecular weight polyethylene liner. Dedicated alignment guides and cutting instruments ensure accurate bone preparation and implant placement. Limited clinical trials commenced in 1992 and expanded to multicenter clinical trials in 1997. Every hip has been monitored with radiostereometry to measure migration to an accuracy of 0.1 mm. All calcar implanted femoral components show excellent function at 4 to 5 years followup, with no migration revealed by radiostereometry.

Animals↗
PubMed1997

Bone tissue reactions to an electrophoretically applied calcium phosphate coating.

Oral implants of a threaded design, calcium phosphate (CaP)-coated using an electrophoretic deposition technique, were compared to uncoated commercially pure (c.p.) titanium control in an animal study with 4 weeks and 6 months of follow-up, respectively. The 3D surface roughness of a CaP-coated implant was about three times greater than that of an uncoated control. Histomorphometric analyses of the direct bone-implant contact demonstrated a short-term advantage to the CaP-coated implants, whereas no significant difference to the uncoated titanium was found after 6 months. Comparison of the amount of bone inside or outside the threads showed similar values for test and control after 4 weeks. Significantly higher amounts of bone outside the uncoated c.p. titanium implants were measured after the long-term follow-up.

Animals↗
PubMed1997

Short- and long-term animal studies with a plasma-sprayed calcium phosphate-coated implant.

A commercially available hydroxyapatite (HA)-coating was investigated in a 4- and 24-week animal study. HA-coated and uncoated commercially pure (c.p.) titanium threaded implants were inserted in rabbit tibia and femur. Qualitative histology showed giant cells and macrophages around both types of implants. Histomorphometry demonstrated significantly more bone in contact to the HA-coated specimens at both follow-up periods. In contrast, bone area measurements (the amount of bone inside and/or outside the threads) revealed significantly higher percentages of bone around the uncoated c.p. titanium controls after 6 months of follow-up. The inferior amount of bone around the HA-coated implants in the longer-term perspective may relate to macrophage-induced resorption.

Animals↗
PubMed1997

A bone-anchored percutaneous connector system for neural prosthetic applications.

A percutaneous connector system has been developed for use in neural prosthetic applications. It is based on a skin-penetrating, bone-anchored titanium pedestal, housing an II-channel electrode array. Initial applications for the system are in audiology and as such, the proposed fixture site is in the temporal bone. The titanium pedestal is based on existing design features of the EPI Bioglass implant, developed by University College London (UCL), and the Brånemark System, employed by Nobel Biocare AB. The electrode array, consisting of platinum wires in a silicone carrier, can be custom designed to suit the application. The design features of the connector system are reviewed. Animal studies have been used to assess soft tissue reactions and the osseointegration of the pedestal. The histological data are presented. The pedestal, electrode array and the mating external connector are currently undergoing mechanical and electrical testing. The percutaneous connector system will undergo clinical trials, initially in the study of tinnitus (employing stimulation via an extracochlear electrode), and as part of a cochlear implant system (using a multichannel intracochlear electrode array and digital signal processing techniques.

Animals↗
PubMed1996

Torque and histomorphometric evaluation of c.p. titanium screws blasted with 25- and 75-microns-sized particles of Al2O3.

A comparison was made between screw-shaped c.p. titanium implants blasted with either 25- or 75-microns particles of Al2O3. The implant surfaces were investigated with respect to topography and composition before implantation in rabbit bone. Grit blasting with 25- or 75-microns particles produced two different surface roughnesses, but no significant difference in the surface composition for the two surfaces. After 12 weeks insertion time in the rabbit tibia and femur, a higher removal torque and more bone-to-metal contact was found for the implants blasted with 75-microns particles compared with the 25-microns-blasted ones.

Aluminum Oxide↗